This invention relates to a seal and more particularly to a seal for a large annular opening.
Seals such as this are utilized in missile launch tubes to control the distribution of eject gas pressure on pressure sensitive areas of the missile surface, as the seal prevents eject gases from leaking up the annulus formed by the launch tube and missile. Since the annulus is spacious in order to provide room for lateral missile motions during shock and launch, large seals which can allow these missile motions while controlling the eject gas are required.
Despite performance which is not entirely satisfactory and predictable, lip-type seals such as shown in U.S. Pat. No. 4,033,593, have been in general use for this application. The reasons for the usage of lip seals include ease of manufacture, installation, and they allow lateral missile excursion while sealing against excessive launch pressure leakage. While such seals have been adequate to withstand the normal launch pressures, their disadvantages include: (1) forces induced in the seal tend to concentrate at specific locations on the attachment surface, raising the possibility of attachment system failure; (2) adverse lateral force differentials are induced in the missile as it becomes offset in the launch tube; and (3) the lip seal will tend to hump up under pressure and may invert if pressure differentials become too high.
Generally speaking, design criteria for large seals of this type include: (1) minimization of destabilizing lateral impulses; (2) generation of stabilizing lateral forces; (3) high reliability; (4) high pressure capability; and (5) minimal performance variability. The unique configuration of the suspended hoop seal provides the potential means to improve seal performance in these areas.